nvestigators searching for missing University of Iowa student Mollie Tibbetts have gotten hundreds of tips and are looking for her in ponds, fields and from the air, officials said Friday morning at a news conference.

“Unfortunately, we have not yet found Mollie, but it has not been due to a lack of effort or a lack of resources,” said Kevin Winker, director of investigative operations for the Iowa Department of Public Safety.

Tips on the missing student “have been coming in regularly,” and 30 to 40 investigators are on the case, Winker said.

The 2-week-old case is “very frustrating, but it hasn’t slowed our efforts,” Winker said, adding that investigators “come to work everyday with the attitude that we’re going to find Mollie.”

Asked whether they’re investigating Tibbitts’ disappearance as an abduction, Winker said they are treating it as a missing person case. He would not say whether investigators have any suspects or persons of interest.